Improvement in tanning leather



UNITED STATES PATENT OFFICE.

H. G. JOHNSON, OF CLEVELAND, OHIO.

IMPROVEMENT IN TANNING LEATHER.

Specification forming part of Letters Patent No. 20,565, dated June 15, 1858.

To all whom it may concern Be it known that I, HORACE Gr. JOHNSON, of Cleveland, in the county of Guyahoga and State of Ohio, have invented new and useful improvements in the process of preparing the hides of animals for the tan and tanning the same into leather and I do hereby declare that the following is a full and complete description of the process and materials employed therein.

The hair of the skin is removed in the ordinary manner by immersion in the lime-vat and the use of the knife and beam; but skins may be tanned by my process without removing the hair. In this latter case they should be soaked in water till they are soft and pliable and worked ofi upon the flesh side. When skins are prepared in the lime-vat, instead of using a bate-vat (composed of a solution of hen-dung) for neutralizing the lime, I use the following-named preparation To thirty gallons of soft water 1 add one pound of common sulphuric acid, six pounds of common salt, and one bushel of wheat-bran. These proportions should be very nearly preserved, though they may be slightly varied without materially changing the results. The ingredients named should be wellstirred togetherin a suitable vessel, and as many skins immersed therein as the liquid will conveniently cover, where they should remain from six to twelve hours, according to the thickness of the skin. Frequent handling in this solution is beneficial. The skins should then be taken out of the solution and worked off on the beam in the usual manner, and they will be ready for the tan.

The tauliquor is prepared in the following manner. Theproportions named should also be very nearly preserved, though no injury would result from slight variations: To one gallon of strong decoction of Aathemz's cotula, of Linnaeus, (Maruta cotala of modern botanists,) one pound of the dry herb to a gallon of water, I add onefourth of a pound of catechu or terra-japonica, two ounces of alum, and two ounces of common salt. This mixture I stir well together,

and immerse in it the skins or hides in the same condition that they came from the beam, as hereinbefore mentioned. The skins, when thus placed in this last-named preparation, should be frequently stirred or handled. Frequent exposure to the air hastens the process of tanning. The time required to convert the skins into leather will vary according to the thickness of the skins and the strength of the tan. With a strength of liquor herein named sheep-skins will become well tanned in from three to six hours at a temperature of 70 Fahrenheit. Calf-skins require from three to six days, and hides for heavy leather will become tanned in from ten to fifteen days. Sole and harness require about twenty days.

Terra-japonica may be used without the 'maruta in the following proportions: To fifteen gallons of soft water add twelve pounds of terra-japonica, one and three-fourth pounds of alum, one and a half pounds of common salt; but I prefer the ingredients and the proportions herein previously named, as it gives the leather a finer color than would be given by either alone; or any other coloring-matter may be added that will not precipitate the tannin of the liquid.

Vhen the skins are sufficiently tanned they should be placed upon a hurdle over the vat to drain, and then smoothed out upon a table and hung up in a cool place to dry. The finishing can be done in the ordinary manner.

WhatI claim as my improvement, and de sire to secure by Letters Patent, is-

The use of the Aathemis cotala, or any other species of marata, either separate or mixed with terra-japonica in any proportion, or combined with alum and common salt, or their chemical equivalents, in the manner and for the purpose set forth, not intending, however, to confine myselfto the exact proportions herein named.

HORACE G. JOHNSON.

Witnesses:

J. S. DOUGLAS, J. BRAINERD. 

